Retroreflective films are characterized by the ability to reflect incident light back toward an originating light source. Cube corner retroreflective sheeting, sometimes referred to as “prismatic” retroreflective sheeting, typically comprises a thin transparent layer having a substantially planar first surface and a second structured surface comprising a plurality of cube corner elements. Each cube corner element is formed by three reflecting faces at the surface of the thin transparent layer. Light incident upon a reflecting surface can undergo a number of additional reflections before being directed back toward the light source. Prismatic retroreflective sheeting may be used in traffic safety applications, such as for license plates, road signs, barricades, pavement markers and marking tape, as well as for personal safety applications including tape for clothing, headgear, vehicles and the like. Prismatic retroreflective sheeting may be used to provide signage in graphic arts applications.
Prismatic retroreflective sheeting is known for being able to reflect a large portion of incident light back towards an originating light source. Without a light source, however, prismatic retroreflective sheeting can be difficult to see under some conditions.
Lightguides are used to facilitate distribution of light from a light source over an area much larger than the light source. Lightguides comprise optically transmissive materials and may have different forms such as slab, wedge, and pseudo-wedge forms. Most lightguides are designed to accept light at an edge surface and allow this light to propagate by total internal reflection between a back surface and an output surface, toward an opposing edge surface from which the light enters. Light is emitted uniformly from the output surface using extracting features that are positioned in various types of patterns on the output surface.